This section provides background information related to the present disclosure, which is not necessarily prior art.
Internal combustion engines, such as gasoline or diesel engines, for example, often have a coolant system to remove heat from the engine that would otherwise have detrimental effects on fuel economy, engine performance, and longevity. Typical coolant systems include at least a pump, a heat exchanger, such as a radiator for example, coolant fluid, and various tubes, hoses, or passages to convey the fluid between the engine and the heat exchanger. Coolant systems can also include a thermostat, which typically blocks coolant flow through the system until the engine warms up to a predetermined operating temperature, and then allows full flow thereafter. The fluid can be pumped through passages in the engine to absorb heat generated by combustion. The heated fluid can then pass through the heat exchanger to release the heat, typically to the atmosphere.
The flow rate of the fluid through the system can be important to ensure optimal cooling of the engine. In order to vary flow rate of the fluid, coolant pumps are typically rotationally driven by a belt connected to a pulley mounted to the engine crankshaft. In this way, the pump speed, and therefore the fluid flow rate, is proportional to the engine speed, i.e. revolutions per minute (RPM). As the engine RPMs increase, the coolant flow rate increases. In some situations, this configuration is preferable in order to roughly correspond cooling capacity with heat production from the engine. However, it has been found that certain high RPM conditions can produce flow rates that exceed the necessary cooling capacity, and/or can be detrimental to various components of the cooling system. Specifically, higher flow rates can lead to increased erosion of the internal passages of the heat exchanger, which can shorten the lifespan of the heat exchanger. The desirable flow rate ranges can vary with application and equipment, but for example some coolant systems have been found to produce flow rates in excess of 450 liters per minute in certain high RPM conditions, while only requiring flow rates in the order of 220 liters per minute.
Prior solutions to regulate coolant flow have typically been complex, costly, or resulted in restricted flow at lower flow rates. For example, some coolant systems use complex valves, other systems use devices that restrict flow at all flow rates, or become closed to flow when certain flow or pressure conditions are exceeded. Other systems are known to decouple the pump operation from the engine speed by utilizing an electrically driven pump. Flow rates of these electric pumps can be controlled based on temperature and flow rate sensors. However, the cost and complexity of such systems can be undesirable. Accordingly, a need exists for an improved internal combustion engine coolant system having low resistance during low RPM conditions, while regulating flow during high RPM conditions.